Skull caps are a traditional head covering worn in accordance with Jewish custom.
The shape of a skull cap can be considered to be a hollow semi-spherical shape. Stated differently, a skull cap has only two outermost or external surfaces, namely an internal concave surface and an external convex surface.
The skull cap is delimited at a peripheral edge at which the concave and convex surfaces meet. Stated differently, a skull cap is devoid of any construction outward from the peripheral edge. For example a skull cap is devoid of a rigid face shading projection comprised by baseball caps.
As the concave surface is hidden when worn, information such as the skull cap size and brand are typically printed on a tag attached to the concave surface or, alternatively, can be printed directly on the concave surface.
Different Jewish factions are known to wear skull caps identifiable to their faction. One faction (known to be called “modern orthodox”) wears a so-called “knitted” skull cap type. Another faction (known to be called “ultra orthodox”) wears a skull cap type comprising two layers of material joined or meeting along a peripheral edge, the outer convex layer of which is made of velvet and the inner layer of which is made of a material other than velvet.
The ultra orthodox faction, which wears the velvet outer layer skull cap, customarily do not use any visible fastening arrangement such as a rigid pin (e.g., a bobby pin) to fasten the skull cap to their head or, more precisely, to their hair (in contrast to the faction who wear the knitted type of skull cap and do use pins). Consequently, the velvet-outer layer skull caps are particularly prone to falling off a wearer's head, especially in windy conditions.